Generate Recamán sequence

recaman.js

/**
 * Generate Recamán sequence up to `maxNum`
 * https://youtu.be/FGC5TdIiT9U
 *
 * @param {Number} maxNum
 * @returns {Set}
 */
function recaman (maxNum) {
  const result = new Set([0])
  let current, hop

  for (current = 0, hop = 1;;hop++) {
    const backwardsHop = current - hop
    const backwardsIsInvalid = result.has(backwardsHop) || backwardsHop < 0
    const next = backwardsIsInvalid ? (current + hop) : backwardsHop

    if (next < maxNum) {
      result.add(next)
      current = next
    } else {
      break
    }
  }

  return result
}